Valmiki Ramayana
In Adi-Kanda of the Ramayana, one reads that the Kambojas, Yavanas, Sakas and some other allied tribes of north-west were 'created' at the request of sage Vasistha by the Divine cow Shavala to defend sage Vasistha from the forces of king Vishwamitra.
This poetical 'creation' of the Kambojas etc. may point to some remote attempt on the part of some Brahmana rishi of Vasistha line to proselytize Iranian Kambojas and other allied clans of the north-west into brahmanised Kshatriyas of the Indo-Aryan version.
These Hinduised Kambojas later became ardent champions of Vedic religion and the great scholars of the Vedas. Kamboja Aupamanyava was a distinguished scholar/grammarian and finds a place in the line of great ancient Vedic teachers of Vamsa Brahmana of Sama Veda. Being a Kamboja and son of Upamanyu, this Kamboja sage was referred to as Kamboja Aupamanyava.
Ludwig, Zimmer, Pusalkar, Law etc. identify sage Upamanyu of Rig Veda with Upamanyu, the father of Kamboja Aupamanyava.
The Hinduised Kambojas are found listed at par with the Vasisthas in Paraskar Grihyam Sutram according to which the Kambojas and Vasisthas had common custom to wear one choti on right side of the head.
This shows that the social and religious customs of the Brahmanised Kambojas and the Indo-Aryan Vasisthas were identical but differed from other scholarly clans of ancient India.
The Bahu/Sagara Puranic legend also testifies very intimate relationship of the Kambojas with the Vasistha clan.
There are several references in Sanskrit and Pali literature which inform us of the scholarship of Kambojas.
The Mahabharta reveals that, besides being fierce warriors, the Kamboja soldiers were also noted as learned people (kritavidyashcha).
The Vasistha clan appears to have played a leading role in proselytising the Persian Kambojas, especially the cis-Hindukush Kambojas living in Kabol, Swat and Rajori region, into Hinduism.
There are further indications that Kaundinya line of Brahminas, an offshoot from Vasisthas, also had good relations with the Kambojas, especially those Kambojas who had settled in western and southern India after Christian era.
See article: Brahmanism of Ancient Kambojas
Read more about this topic: Kambojas In Indian Literature